Wide bandgap semiconductor materials (with Eg>2 eV) such as silicon carbide (SiC) or Group III nitride compound semiconductors (e.g., gallium nitride GaN) are very attractive for use in high-power, high-temperature, and/or radiation resistant electronics. SiC power rectifiers and RF transistors are now commercially available, and SiC power switches as well as GaN microwave transistors are expected to appear in the commercial market in the near future.
Under the present circumstances, more compact semiconductor devices with lower losses are preferable in order to meet future demands for higher power. Group III nitrides are widely known to emit light ranging from UV to the visible spectra. Many group III nitrides, therefore, show potential as opto-electronic light sources and high frequency power devices. Although group III nitrides have been shown to be useful in opto-electronic light sources and high frequency power devices, a need exists to make smaller and more powerful devices from group III nitrides to meet the increasingly difficult demands from the resulting devices' performance.
One method of controlling the performance of the device is by doping at least one layer of the substrate, specifically the group III nitride epilayer. In the past, D. Qiao et. al [D. Qiao, Z. F. Guan, J. Carlton, and S. S. Lau and G. J. Sullivan, “Low resistance ohmic contacts on AlGaN/GaN structures using implantation and the “advancing” Al/Ti metallization”, Appl. Phys. Lett., Vol. 74, No. 18, May 1999] and Y. Irokawa et. al [Y. Irokawa, O. Fujishima, T. Kachi, S. J. Pearton and F. Ren, “Activation characteristics of ion-implanted Si+ in AlGaN”, Appl. Phys. Lett. 86, 192102 2005] have demonstrated doping of AlGaN epilayers by ion implantation. However, these processes required a high temperature (greater than 1100° C.) annealing to reduce the implantation induced defects. The annealing conditions depend strongly on the dose and energy of implantation.
Thus, a need exists for a doping process that avoids the potential damage caused by implantation and requires only a moderate temperature annealing. Additionally, a need exists to remove the necessity of depositing encapsulation material to protect the surface from decomposition.